The present invention relates to the making of cheese, and particularly to the making of cheese ripened for two or more months such as Cheddar and Colby cheese.
Milk from many different mammals is used to make cheese, though cow's milk is the most common milk for cheese. Generally, cheese is made by developing acidity in milk and setting the milk with a clotting agent, such as rennet. The set milk is cut and whey is separated from the resulting curd. The curd may be pressed to provide a cheese block. The cheese-making process is essentially a concentration process that captures a portion of the protein, minerals, fat, water, and other minor components present in the original milk component. Rennet-based cheeses include cheeses such as mozzarella, Cheddar, Swiss, and Colby cheese. In a typical Cheddar cheese, the concentration factor is about ten times, i.e., approximately 10 lbs of natural Cheddar cheese are produced from 100 lbs of milk, with the remaining (90 lbs or so per 100 lbs milk) of material removed in the whey byproduct. Typical Cheddar cheese has 1.4 g lactate per 100 g and contains 37.5% water.
Curing typically takes place over a lengthy period of time under controlled conditions. Cheddar cheese, for example, is cured for a period of at least four months and may be cured for a period in excess of one year to obtain the full flavor desired in cheddar cheese.
In contrast to the natural cheese-making process, process cheese is not manufactured directly from milk and process cheese manufacture does not produce any byproducts. Process cheese is produced by combining natural cheese, other dairy based ingredients, water and emulsifying salts into a blend that is subsequently heated (typically to at least 65.5° C. for not less than 30 seconds, see 21 C.F.R. 133.169) and mixed to produce a homogeneous product.
Recently, use of concentrated milk as the base ingredient for making cheese has become more popular. Milk can be concentrated prior to cheese making using a variety of techniques including ultra-filtration, micro-filtration, vacuum condensation, or the addition of dry milk solids such as nonfat dry milk. The use of concentrated milk provides increased efficiency to the cheese-making process. Use of concentrated milk also reduces the amount of whey produced for a given amount of cheese, facilitates standardization of formulation and production, and promotes more consistent quality and yields of the resultant cheese. The use of concentrated milk thus lowers cost and processing times for making cheese, particularly beneficial for semi-continuous cheese manufacturing processes such as utilized in typical large-scale cheese plants. The semi-continuous cheese manufacturing includes numerous cheese vats that sequentially feed a draining/conveying belt and a salting belt. This semicontinuous cheese making system requires consistent and rapid production of acid by starter cultures used in the cheese manufacturing process. The efficiency of semi-continuous cheese manufacturing is substantially improved if the milk is concentrated prior to cheese-making.
During the aging process, calcium lactate crystals can grow within and on the surface of cheese. These crystals are small white spots that can be seen, often without magnification, upon close inspection of the cheese. The crystals are not present in the cheese immediately after manufacture, but typically start to appear between two and six months of aging. While the calcium lactate crystals are not harmful to consumers, they can be perceived in mouthfeel as adding a slight amount of grittiness to the cheese. More importantly for affecting cheese sales, consumers often believe the crystals are mold. The growth of calcium lactate crystals is thus viewed as a defect representing substantial financial loss for cheese manufacturers.
For reasons that are not entirely clear, the use of concentrated milk and a semi-continuous cheese making process in making an aged cheese seems to worsen the calcium lactate crystal problem. Consequently cheese manufacturers have an unenviable choice: they can either use a less efficient cheese-making process or they can use a more efficient manufacturing process that more likely results in calcium lactate crystals defects.
Factors influencing the formation of calcium lactate crystals have been extensively studied. Concentrations of calcium and lactate ions existing in cheese serum are very close to saturation, and small increases in the concentration of either component could result in super saturation and crystallization. It has also been theorized that milk citrate levels and the subsequent utilization of citrate by microorganisms may play a role in calcium lactate formation. Curd washing, curing, and storage temperature may further contribute to calcium lactate crystal formation. Other studies report that calcium lactate is formed when L (+)-lactate is converted into a racemic mixture of L(+)- and D(−)-lactate, the latter being much more prone to crystallization. The conversion of L(+)-lactate to D(−)-lactate is thought to be carried out by certain strains of bacteria.
Prior art methods for limiting calcium lactate crystal formation in cheese include: 1) reducing the concentration of lactic acid in the final curd, 2) reducing or eliminating undesirable non-starter lactic acid bacteria (“NSLAB”) from the cheese-making process, 3) controlling storage temperature, and 4) vacuum packaging cheese to minimize the airspace around the outer cheese surface. The use of certain starter culture strains may also increase or decrease the presence of calcium lactate crystals, due to post manufacture fermentation by the selected starter culture.
Although progress has been made in developing strategies for prevention of calcium lactate crystals, the defect is still prevalent. Better methods of minimizing calcium lactate crystal formation in aged cheeses are needed.